Exercise weight structure

ABSTRACT

A method of producing an exercise weight structure comprises mixing a particulate material with a binder material and moulding the resulting mixture to an appropriate shape. An outer skin for the exercise weight structure is firstly formed of a resilient material, and forms a mould into which an inner weight section or body is moulded or cast. The inner weight section and the outer skin are both formed of recycled material and include a common binder material.

The present invention relates to an exercise weight structure, and in particular an exercise weight structure that may be used as a free weight disc or as a weight body for a dumbbell, barbell or other handle exercise device.

A known exercise device including a weight body structure is disclosed in EP1867365. In the arrangement disclosed in this prior art document an inner weight section or core body of cast iron is cast about an axial securing sleeve. The sleeve provides an interference fit between the weight body and the end of a bar handle. An outer skin of rubber or polyurethane is subsequently moulded around the exterior of the cast iron section. EP 867365 describes how an arrangement including a low grade cast iron core body cast around an axial securing sleeve can provide an improved arrangement. The present invention addresses other issues.

Typically the cast iron used for weight bodies is of low grade or quality enabling the manufactured weight structures to be priced sufficiently economically. Due to the materials used, the weight tolerances for these low to mid range free weight products are wide, and not as tight as those used in competition or high quality Olympic discs which are generally manufactured from steel, which provides better weight accuracy but is more expensive.

The processing of Cast Iron involves very high temperatures which requires large amounts of energy and also requires the use of sand based moulding processes which are, by their nature, very dirty and unpleasant to use.

Also, the cost of transportation by ocean freight of weight based products over long distances is becoming more expensive and is not considered to be environmentally friendly where large tonnages are concerned. It is more ideal to manufacture as close to the end consumer as possible. However, in the case of Cast Iron based free weights this is often not possible because of the associated local high labour costs and the unpleasant nature of the process.

One additional requirement in the production of free-weights is the use of rubber (usually black) to cover the low grade Cast Iron so that in can be used in clean and user friendly environments such as modern gyms or homes. The rubber based coverings are more tactile and will not damage equipment, delicate floorings or furnishings in the way that metal products would. The process of coating the free-weights in rubber also consumes energy and is a dirty and unpleasant process.

Therefore, for reasons identified above, it would be more desirable if a cleaner process, requiring very little energy and providing greater weight accuracy could be utilised. Such a process would allow reduce costs the manufacturing plant to be brought closer the end user.

The invention is as defined in the appended claims.

According to one aspect the invention provides a method of producing an exercise weight structure from particulate material mixed with a binder material and moulded to the appropriate shape. The invention also provides an exercise weight structure so produced.

According to another aspect, the invention provides a method of producing an exercise weight structure by means of first forming an outer skin for the exercise weight structure of a resilient material, the outer skin forming a mould into which an inner weight section or body is moulded or cast.

The first and second aspects are not mutually exclusive and indeed may beneficially be combined such that the invention includes a method of producing exercise weight structure by means of first forming an outer skin for the an exercise weight structure of a resilient material, the outer skin forming a mould into which an inner weight section or body is moulded or cast, the inner weight section or body being of recycled material when mixed with a binder material.

In another aspect of the invention there is provided a method of forming an exercise weight structure comprising forming a first outer shell section and a second outer shell section; filling at least one of the outer shell sections with a particulate material mixed with a binder material; combining the outer shell sections to form an enclosure encapsulating and moulding the particulate and binder mixture. The inner core defined by the particulate and binder mixture bonds to both outer shell sections thereby fixing the outer shell sections in position relative to each other and the core.

The invention will now be further described by way of example only and with reference to the accompanying drawings, and a flowchart describing the manufacturing process and sequence of operations:

FIG. 1 shows an exercise device utilising a weight structure in accordance with the invention. In this example, the weight structure is moulded around a central bush which may have projections or indentations to assist in securing the bush to the weight structure once it has cured and set. The internal bore of the bush can be machined prior to the moulding to provide an interference or sliding fit with the handle;

FIG. 2 shows a similar exercise device in accordance with the invention. In this example, the weight structure is moulded around a central bobbin constructed as a central bush and two integral side plates or washers. The bobbin helps to strengthen the bore whilst giving some support to the side faces of the weight structure;

FIG. 3 shows a similar exercise device in accordance with the invention. In this example, the weight structure is moulded directly onto the handle;

FIG. 4 shows a method of manufacturing a weight for exercise according to an embodiment of the invention; and

FIG. 5 shows a two part outer shell formed by a moulding process according to an embodiment of the invention in preparation to receive the weighted internal material.

Referring to FIG. 1, there is shown an exercise device 1 of generally similar construction to the prior art exercise weight structure disclosed in EP1867365, but differing in certain key aspects.

The exercise device 1 of FIG. 1 comprises a bar 3 having end portions 4 at each end. The exercise device 1 further comprise an exercise weight structure 5 which is mounted on an end portion 4 of the bar 3, with a second weight assembly mounted on the opposite end of the bar. The central portion of the bar comprises a handle portion 6. The exercise weight structure 5 is axially retained on an end portion 4 of the bar 3 in one direction by a locating member 10. The locating member 10 may be a projection, such as a flange, or a collar. Preferably, a washer 11 is provided between the locating member 10 and the exercise weight structure 5. The washer 11 is preferably formed of hardened steel and acts to distribute the load from the locating member over a wider surface area of the inner surface of the weight assembly, as well as improving the surface contact between the locating member and the weight assembly, thereby reducing any wobble between the bar 3 and the an exercise weight structure 5.

The exercise weight structure 5 comprises an inner weight core 7, and an outer skin 8. In this embodiment both the outer skin and the inner core section are formed from recycled or reclaimed waste material. In the case of the outer skin material, the recycled or reclaimed material may comprise, for example, rubber particulate material such as ground rubber particles or granules of rubber waste from tyres or industrial conveyor belts or vehicle timing belts. The rubber particulate material is mixed with a resin binder material, typically a polyurethane resin binder. Typically the particulate rubber material is provided in a batch and the resin is mixed in the appropriate quantity to provide a paste or sludge with the particles distributed throughout the volume in the binder material. The appropriate mix for the binder to particle volume ratio and the particle size can be arrived at by trial and error. A suitable particle size of rubber particle has been found to be from 180 microns with a range up to and up to 3 mm×20 mm square section. The resin binder needs to be added to the rubber particles in percentages of 7.5% to 20% by weight.

In the case of the inner core material, high density particulate or powdered waste from scrap metal or otherwise can be used to form the inner core. Materials such as magnetite, recycled scrap steel, scrap chilled cast iron, or powdered lead waste (such as from lead batteries) may be used. Non metallic high density waste may also be used provided the appropriate overall density for the inner core can be arrived at.

The high density particulate or powdered waste material is mixed with a binder material, typically a polyurethane resin binder. Typically the high density particulate or powdered waste material is provided in a batch and the resin is mixed in the appropriate quantity to provide a paste or sludge with the particles distributed throughout the volume in the binder material. The appropriate mix for the binder to particle volume ratio and the particle size can be arrived at by trial and error and is dependent upon the high density waste material used. A suitable metal particle size for the inner core can be between 0.6 mm to 2.4 mm with a resin percentage of 5% to 20% by weight. Heat at low temperatures may be used to accelerate the curing process.

The outer skin 8 protects the inner weight section from damage and corrosion, as well as providing an aesthetically pleasing finish. A central bore 2 is formed in the weight assembly for receiving the end portion 4 of the bar 3. The use of the outer skin 8 in combination with the inner core 7 is not necessary in all embodiments and the invention may extend no further than the use of the inner core 7 formed in accordance with the invention as a an exercise weight structure. Additionally, an inner core of particulate/recycled material held by means of a binder may be provided with an outer skin of a resilient material (e.g. polyurethane or rubber) not comprising particulate material held by a binder. The skin prevents the composite inner core from cracking due to shock impact for example when dropped onto a hard surface.

Where the inner core 7 and outer skin 8 are both formed of waste material it has been found that it may be beneficial to use the same resin binder material for both the outer skin 8 and the inner core 7.

In accordance with an aspect of the invention an exercise weight structure is produced by means of first forming an outer skin for the an exercise weight structure of a resilient material, the outer skin forming a mould into which an inner weight section is moulded or cast.

In practice this can be achieved by means of lining an appropriately shaped mould cavity with a skin material (which may comprise a sludge or paste of recycled resilient—e.g rubber-granules held by means of a resin binder—e.g. a polyurethane binder). An inner mould block being a facsimile of the core may be introduced into the mould cavity in order to apply pressure to the lining skin layer 8 and mould the internal surface of the lining skin layer to the appropriate shape. The application of pressure in this way also ensures that the required density for the lining skin layer 8 is achieved. Alternatively, it has been found that the natural expansion of the polyurethane material when combined with the binder may be sufficient for the skin material to fill the mould and provide the required skin density.

The inner mould block is then removed and the high density mix for the core 7 (i.e. the high density waste metal material mixed with the resin binder) is then introduced (typically poured) into the mould cavity formed by the inner surface of the outer lining skin 8. The core material is then compressed by the application of a pressure piston or ram and the material is allowed to cure either at ambient temperature, or in an oven at elevated temperature. The resin from the high density mix fuses with the resin in the outer lining skin 8 as it cures and hardens, which provides improved bonding between the skin and the core. In some cases, particularly with larger sizes of dumbbells, it may be necessary to include a third operation in order that the outer face of weight structure 5 can receive an outer covering of resilient material which is not covered by the end plate 12. In this case a further layer of lining material is poured into the mould and compressed to provide a partial top coating to the weight structure 5 before the end plate 12 is fitted.

The high density mix for the inner weight core 7 and the resilient material mix for the skin 8 are carefully pre-processed before being introduced into the mould, by weighing and accurately dosing and mixing the constituent materials.

In an embodiment of the invention, the manufacturing process for a dumbbell comprises the following steps:

-   -   (1) Outer mould is cleaned and prepared for use;     -   (2) Inner mould (facsimile of the inner weighted core section)         is cleaned and prepared for use.     -   (3) Materials for producing the outer skin of the weighted         structure are prepared and individually weighed out according to         the recommended mix identified below and to the required volume.         These material include recycled and granulated polymers and a         binding resin;     -   (4) Materials of step 3 are thoroughly mixed together adding any         trace accelerators if required;     -   (5) A portion of the resultant mixture is poured into the base         of the mould;     -   (6) The inner mould is located into the outer mould;     -   (7) The remainder of the outer skin recycled polymer mix is         poured into the mould and compressed for a short period of time;     -   (8) The inner mould is removed once the outer skin mixture has         started to set;     -   (9) The materials required to produce the inner section of the         weighted structure, including recycled and granulated polymers         and binding resin are prepared and individually weighed out         according to the recommended mix identified below and to the         required volume;     -   (10) The ingredients of step 9 are thoroughly mixed together         adding any trace accelerators if required;     -   (11) The inner bush, collar or bobbin is located into the centre         of the mould;     -   (12) The mixture of step 10 is poured into the mould previously         formed by the outer skin mixture;     -   (13) The mould and contents is preferably compressed for a short         period of time and the contents left to cure; and     -   (14) The mould is taken apart and the weighted structure         comprising of an inner bush, inner weighted section and outer         skin is removed.

In an embodiment a collar 16 is provided internally of the core 7, for receiving the end portion 4 of the bar 3. The collar 16 is located between the end portion 4, and the core 7. The collar 16 is preferably cylindrical, and surrounds the periphery of the end portion 4. Preferably, the collar 16 extends along the entire length of the central bore 2 of the weight assembly 5. The collar is preferably formed from seamless mild steel tubing, but may also be formed from any other suitable material.

The collar 16 may be easily machined to tight tolerances, and may be provided with a smooth surface finish. As such, an interference fit may be provided between the end portion 4 and the collar 16, to prevent or limit movement therebetween. In particular, the interference fit prevents relative axial and rotational movement between the end portion 4 and the collar 16. In this way, the collar 16 provides a securing member, which has the advantage of obviating the requirement for threaded fastenings. However, any form of threaded fastening can be used in conjunction with the collar. And the collar may itself be formed with an internal thread which could match with a threaded portion machined into the end portion 4 as an alternative method for fixing.

The collar 16 is provided to prevent movement between the end portion 4 and the weight assembly 5. Therefore, as well as achieving a suitably toleranced fit between the collar 16 and the end portion 4, it is also necessary to ensure that any movement between the collar 16 and the weight assembly 5 is prevented. For the reasons discussed above in relation to the end portion 4, it may not possible to machine a bore in the inner weight core 7 suitable for providing a close fit with the collar 16.

Therefore, the inner weight core 7 is formed by moulding around the collar 16 during the moulding process. The collar 16 is therefore positioned internally of the mould at least before the high density mix for the core 7 (i.e the high density waste metal material mixed with the resin binder) is introduced into the mould cavity formed by the inner surface of the outer lining skin 8. As such, the inner weight core 7 forms to the outer surface of the collar 16. The collar obviates the need for subsequent machining of the inner weight core 7. Furthermore, the closest possible tolerance between the collar 16 and the inner weight core 7 is achieved, which prevents lateral movement therebetween.

The collar 16 comprises a longitudinal axis, as shown by line A-A in FIG. 1. The longitudinal axis of the collar 16 is coaxial with the longitudinal axis of the bar 3 when the weight assembly 5 is mounted on the end portion 4. To prevent relative axial movement between the collar 16 and the weight assembly 5, a portion of the inner weight section 7 extends into the collar 16, or vice versa. Preferably, the collar is provided with one or more keying formations such as at least one annular channel 18. The channel 18 is machined into the outer surface of the collar 16, and preferably extends around its entire periphery. During the moulding process, the high density mixture fore the weight core 7 penetrates into the channel 18 and solidifies. The inner weight section 7 is thus formed such that a portion of the inner weight section 7 extends into the collar 16. The interaction between the channel 18 and the portion of the inner weight section 7 extending into the collar 16, prevents axial movement between the inner weight section 7 and the collar 16. In the embodiment of the invention shown in FIG. 3, the collar 16 is provided with three channels 18, although such is not essential and other numbers may be provided. The collar 16 may also be provided with channels 18 extending along its length to prevent rotational movement between the collar 16 and the weight assembly 5.

A first securing member is provided to secure the weight assembly 5 to the end portion 4. The first securing member may comprise an end plate 12. The end plate 12 secures the weight assembly 5 to the end portion 4 independently of the collar 16. It is necessary to provide a securing member in addition to the collar, as for all but the lightest of weights, an interference fit is not sufficient to permanently secure a weight on a dumbbell bar. Preferably, the end plate 12, comprises a load bearing plate (not shown), and an outer skin. The outer skin is moulded around the load plate in a similar manner to the outer skin 8 of the weight assembly 5.

The end plate 12 further comprises a central aperture 26. The end plate 12 covers a recess 21 in the outer skin 8 of the weight assembly 5, with the peripheral edge of the end plate 12 supported by the outer skin 8. The end plate 12 is further supported about the central aperture by a first projection 17 extending from the end portion 4. Preferably, the first projection 17 is of reduced diameter relative to the end portion 4. A second projection 19, of reduced diameter relative to the first projection 17, extends from the first projection 17 and within the central aperture 26.

The second projection 19 may comprise a bore 15 extending through its centre, as shown in FIG. 6 a. The bore 15 may extend downwards into the first projection 17, and into the main body of the end portion 4. The bore 15 is provided to receive the spigot 13 of the number disc 9. The disc 9 may be used to display information relating to the weight of the dumbbell, logos, or other information or designs. The spigot 13 extends from the rear surface of the disc 9, and is received by the bore 15. The end plate 12 may comprise a recess 26 for receiving the disc 9, such that the disc 9 is flush with surface of the end plate 12. The disc 9 obscures the weld 20, and second projection 19 from view. In the same way, the end plate 12 obscures the end portion 4 from view.

The end plate 12 is secured to the end portion 4 of the bar 3. In one embodiment, the end plate 12 is secured to the end portion 4 by a weld 22. The weld is formed in the central aperture 26 of the end plate 12, and surrounds the second projection 19. Preferably the central aperture 26 is tapered, or counter-sunk to retain the weld more securely. The weld 26 provides a permanent fixing, and obviates the need for a threaded fastener such a locking nut or a countersunk screw, however, a threaded faster could be used in applications where welding is not permissible such as when there is a danger that the resilient coating could be adversely affected by the application of heat at this stage. Previously, it has not been possible to use a weld to permanently fix the weight assembly of a dumbbell, as movement between the end portion of the bar and the weight assembly would result in the weld cracking. However, the present invention provides a collar 16 which is cast into, and fixed relative to, the weight assembly 5, and which provides an interference fit with the end portion 4. As such, movement between the end portion 4 and the weight assembly 5 is prevented, thereby enabling the use of welds as a permanent fixing means. In a further advantage, by obviating the requirement for threaded fastenings, it is no longer required to provide the inner weight section 7 with a recess to accommodate the fastening below the upper surface of the weight assembly 5.

In an alternative embodiment shown in FIG. 2, the weight core 107 is moulded around a central bobbin 116, which replaces the collar 16 of the previous embodiment. The bobbin 116 comprises a central bush 132 and end plates or flange sections 132 at either end. The end plates 132 are integrally formed with the bush 120. The bobbin 116 obviates the requirement for a separate washer and helps to strengthen the bore whilst giving some support to the side faces of the weight structure. In addition, the bobbin 116 improves the moulding process by preventing flow of core material into the cavity defined by the outer skin 108 on the inner face of the weight section 105. In a yet further arrangement shown in FIG. 3, the weight core 205 may be moulded directly to the end portion 204 of the bar 203.

In a further embodiment as shown in FIG. 5 the outer skin 308 is formed as a two part component. In the arrangement shown in FIG. 5 the weight device 300 is a weight disc, but the same may apply to a weight head for a dumbbell. The outer skin 308 includes an upper section 320 and a lower section 322. The upper section 320 and lower section 322 are formed as a ‘up’ and ‘lid’ arrangement, with the lower section 322 having a greater depth to receive the majority of the core material and the upper section 320 acting to close of or cap the lower section 322 and having a lesser depth in the axial direction. The upper 320 and lower 322 section may be formed in the same injection moulding process as described above, but with the two components having dedicated mould tools. Following formation of the upper and lower sections the core material is poured into the lower section 322, levelled off and the upper section 320 then applied to close the lower section 322, with the upper 320 and lower sections 322 effectively defining a ‘clam shell’ type mould arrangement with both sections being retained within their respective moulds. The upper and lower sections are then clamped together while the core material cures. The natural expansion of the core material is sufficient to ensure that the mould defined by the outer skin 308 is filled completely, and an additional pressure may be externally applied to assist in the filling operation and to ensure that a required density is achieved. The bonding between the common binder in the core and outer skin materials locks the outer skin to the core and, in combination with the clamping of the outer skin 308, is sufficient to hold the upper 320 and lower 322 shell sections together without a further seam joining operation being required to fuse the two sections. 

1. A method of producing an exercise weight structure comprising: mixing particulate material with a first binder material; and moulding the resultant mixture to shape.
 2. An exercise weight structure comprising a particulate material mixed with a binder material.
 3. The structure according to claim 2, wherein the particulate material comprises one or more of recycled, reclaimed and waste material.
 4. The structure according to claim 2, wherein the particulate material comprises a metallic material.
 5. The method according to claim 1, wherein the particulate material comprises one or more of recycled, reclaimed and waste metal.
 6. The structure according to claim 2, wherein the material comprises a resin material.
 7. The structure according to claim 6, wherein the resin material comprises a polyurethane material.
 8. The method according to claim 1, further comprising curing the particulate material mixed with the first binder material to form the exercise weight structure.
 9. The method according to claim 1, further comprising introducing the particulate material mixed with the first binder material into a mould and moulding to shape.
 10. The method according to claim 9, further comprising applying pressure to the mould.
 11. The method according to claim 1, further comprising forming an outer skin layer, the outer skin layer at least partly covering a core of the particulate material mixed with the first binder material.
 12. The method according to claim 11, further comprising lining a mould with the outer skin layer and introducing the particulate material mixed with the first binder material into the mould.
 13. The method according to claim 11, wherein the outer skin layer is resilient.
 14. The method according to claim 11, wherein the outer skin layer is selected from the group consisting of rubber and polyurethane material.
 15. The method according to claim 11, wherein the outer skin layer comprises a resilient material in particulate form mixed with a second binder material.
 16. The method according to claim 15, wherein the resilient material comprises a waste material.
 17. The method according to claim 15, wherein the first binder material and the second binder material are the same material.
 18. The method according to claim 11, further comprising forming the outer skin layer as two separate parts, the two separate parts defining a mould for forming the core.
 19. The structure according to claim 2, wherein the exercise weight structure includes a collar permitting mounting on a shaft or bar, the particulate material mixed with binder material being shaped about the collar.
 20. A method of producing an exercise weight structure comprising: forming an outer skin for the exercise weight structure, the outer skin forming a mould cavity; and forming an inner weight body in the outer skin by one or more of molding and casting.
 21. An exercise weight structure comprising an outer skin for the exercise weight structure, the outer skin forming a mould cavity with an inner weight body disposed in the mould cavity.
 22. The structure according to claim 21, wherein the outer skin is resilient.
 23. The structure according to claim 21, wherein the outer skin comprises rubber or polyurethane material.
 24. The structure according to claim 21, wherein the outer skin comprises a resilient material in particulate form mixed with a binder material.
 25. The structure according to claim 24, wherein the resilient material comprises a waste material.
 26. The structure according to claim 25, wherein the binder material is a curable binder.
 27. The structure according to claim 21, wherein the exercise weight structure includes a collar permitting mounting on a shaft or bar, the weight body being shaped about the collar.
 28. The method according to claim 20, further comprising forming the outer skin by moulding. 